It is common known and seen that espresso machines or coffee makers equipped with a steam tube with nozzle to inject steam air into milk in a liquid container such as milk mug or milk jar. The effect of injecting steam air into milk is to heat up the milk and froth the milk to produce milk foams. The steam tube normally has one steam nozzle or steam tip. The steam nozzle has at least one steam hole allowing steam to be emitted from the inside of the steam tube, through the steam hole, and into the liquid container. The steam hole normally is a round shape hole, but it can be in other shape, such as triangle, square, and oval. When froth milk, the steam nozzle is submerged into the liquid container and allows the steam to mix and stir the milk.
When frothing milk, it is important to swirl and fold the milk in a circular motion in order to produce a smooth, even consistency and texture of foams. If there is no swirl and folding in a circular motion, the air and milk does not fully incorporate into each other, which will produce low quality frothed milk with large separated bubbles.
The conventional structure steam nozzle normally is configured with steam hole(s) oriented axially the steam tube. The steam exiting the steam outlet only in an axial direction into the liquid container with milk. This conventional design has several disadvantages that the direct stirring and/or heating area is relatively small and the steam hit the bottom of the liquid container directly. As a result, the conventional steam nozzle will only has vertical regional flow, which will not create a circular motion along the liquid container that folds and swirls the milk to produce good milk foams.